1. Field of the Invention
This invention relates to a method for improving the strength of water-saturated soft soils.
2. Description of the Prior Art
It is generally known from past experience that a water-saturated soft soil deposited on the bottom of seashore, river, lake and lagoon must be strengthened to enable passage of people or traffic vehicles or conveyance of construction machines on reclaimed soft grounds formed by dredging such water-saturated soft soil.
In U.S. Pat. No. 4,299,516 owned by Chiyoda Chemical Engineering & Construction Co., Ltd., there is disclosed a method in which such a soft soil is treated with a specific additive for improving the strength thereof by reaction between various components of the soil and the additive. More specifically, in this prior art method, the soft soil is admixed with ingredient A including gypsum and ingredient B including a mixture of a water-granulated iron blast furnace slag and a Portland cement, with a ratio by weight of ingredient A to ingredient B being in the range of 10/90 to 30/70. This prior art suggests the desirability that the total amount of ingredients A and B be 50-150 kg per cubic meter of the soft soil to be treated and that ingredient A be admixed with the soft soil before ingredient B.
While this prior art method may impart a desirable strength to the soft soil, the method encounters certain problems in operational efficiency, especially when applied to the large scale treatment of soft soil. That is, the prior art method is not quite satisfactory in ease of attaining the homogeneous mixing of ingredients A and B with the soft soil, which is essential to effectively increase the strength of the soft soil. Thus, with this method, it is necessary to continue the mixing operation for a relatively long period of time or to conduct a high load mixing operation in order to impart a practical acceptable strength to the soft soil.